This application is for funds to carry out a second and third round of interviewing with a sample of women originally interviewed in 1971. The aims are to describe and explain differences with respect to sexuality, contraceptive behavior, pregnancy and marriage in this population. Support for further analysis of data from the original survey is also requested. Emphasis is placed on the advantages of a longitudinal approach for the detection of the causal directions and for the more precise identification of trends. By the third round the original group will be 20-24. Thus it is proposed also to draw a limited sample in the final year of females aged 15-19 for comparison with the original group in terms of the same basic items of behavior: prevalence of intercourse, knowledge and use of contraception, pregnancy, marriage, expected family size, attitudes toward abortion and illegitimacy.